<!doctype html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>tab</title>
    <link rel="stylesheet" href="index.css">
</head>
<body>
    <div class="div1">
        <ul class="a">
            <li>推荐</li>
            <li>导航</li>
            <li>视频</li>
            <li>购物</li>
        </ul>
         <div>
             <div>推荐</div>
             <div>导航</div>
             <div>视频</div>
             <div>购物</div>
         </div>
            </div>
            <script>
                var a1 = 10;
                var a2= 20;
                alert("a1+a2"=+a1+a2);

            </script>
</body>
</html>
                       